Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels, such as by employing a stent. Stents act as scaffoldings, functioning to physically hold open and, if desired, to expand the wall of affected vessels. Typically stents are capable of being compressed, so that they can be inserted through small lumens via catheters, and then expanded to a larger diameter once they are at a desired location. Examples in the patent literature disclosing stents include U.S. Pat. No. 4,733,665 issued to Palmaz, U.S. Pat. No. 4,800,882 issued to Gianturco, and U.S. Pat. No. 4,886,062 issued to Wiktor.
Conventionally, stents are delivered to the desired location by crimping the stent tightly onto a balloon catheter and transporting the crimped stent/balloon catheter combination to the desired location through a patient's vasculature. Alternatively or in addition to the crimping, the balloon catheter is expanded to contact the inner diameter of the stent. At the desired location, the balloon catheter is expanded, thereby expanding the stent to contact the inner diameter of the patient's artery. The balloon catheter is then deflated and removed from the vasculature.
Since the stent and catheter travel through the patient's vasculature, the stent must have a small diameter so that it can pass through small lumens of the patient's vasculature. Secure attachment to the catheter is desirable so that the stent does not prematurely detach from the catheter. The stent should also be sufficiently flexibility to travel through curvatures in the patient's vasculature.
However, conventional crimping techniques can be uneven, leading to sharp edges on the crimped stent that can damage or get caught on the patient's vasculature during delivery. Further, crimping can decrease flexibility of the stent, making it hard to deliver the stent through curvatures in the patient's vasculature.
If the balloon catheter is expanded before delivery, the balloon catheter may cause excessive expansion of the stent, thereby making it hard to transport the stent through the patient's vasculature (e.g., cross tight lesions). Further, expansion of the balloon catheter can cause the distal and proximal ends of the stent to expand further than the rest of the stent, causing the distal and proximal ends to have upward tapered edges that can get caught in the patient's vasculature, thereby decreasing deliverability.
Accordingly, improved methods and devices are desirable for gripping a stent to a balloon catheter that reduce or eliminated the deficiencies mentioned above.